1. Field of the Invention
The embodiments of the present invention relate generally to miniaturized spectroscopy systems and porous silicon light sources.
2. Background Information
The ability to detect and identify trace quantities of analytes has become increasingly important in many scientific disciplines, ranging from part per billion analyses of pollutants in sub-surface water to analysis of treatment drugs and metabolites in blood serum. Additionally, the ability to perform assays in multiplex fashion greatly enhances the rate at which information can be acquired. Devices and methods that accelerate the processes of elucidating the causes of disease, creating predictive and/or diagnostic assays, and developing effective therapeutic treatments are valuable scientific tools.
Among the many techniques that can be used for chemical analyses, surface-enhanced Raman spectroscopy (SERS) has proven to be a sensitive method. A Raman spectrum, similar to an infrared spectrum, consists of a wavelength distribution of bands corresponding to molecular vibrations specific to the sample being analyzed (the analyte). Raman spectroscopy probes vibrational modes of a molecule and the resulting spectrum, similar to an infrared spectrum, is fingerprint-like in nature. As compared to the fluorescent spectrum of a molecule which normally has a single peak exhibiting a half peak width of tens of nanometers to hundreds of nanometers, a Raman spectrum has multiple structure-related peaks with half peak widths as small as a few nanometers.
The development of new classes of nano-reporters for molecular detection and biological assays, such as for example, composite organic inorganic nanoclusters (COINS), has driven the need, in part, for increasingly miniaturized and cost-effective spectroscopy systems to take advantage of a variety of possible applications of these nano-particle reporters. COINs are composed of metal nanoparticle clusters and at least one organic Raman-active compound. Interactions between the metal of the clusters and the Raman-active compound(s) enhance the Raman signal obtained from the Raman-active compound(s) when the nanoparticle is excited by a laser.
Currently, most Raman spectroscopy systems are bench-top devices. Such devices are typically comprised of expensive components such as: a laser excitation source, a microscope and other optics, a spectrometer, and a large detector. The size and cost of these Raman systems can function as a prohibitive barrier to applications of nanoparticle reporters such as COINs. Miniaturized spectroscopy systems potentially have applications, for example, as elements of field, home, and office diagnostic tests for medical and environmental testing and monitoring.
To obtain a Raman spectrum, typically a beam from a light source, such as a laser, is focused on the sample generating inelastically scattered radiation which is optically collected and directed into a wavelength-dispersive spectrometer. Although Raman scattering is a relatively low probability event, SERS can be used to enhance signal intensity in the resulting vibrational spectrum. Enhancement techniques make it possible to obtain a 106 to 1014 fold Raman signal enhancement.